_Mr. Weld Taylor's Process._--As I presume the object of publishing
Photographic Notes, &c., is to aid those who are _not proficients_ in the
processes indicated, MR. WELD TAYLOR must not take umbrage at his first
communication being misunderstood, whether unavoidably or wilfully, as I am
sure the former must have been the case with all novices in the
photographic art at least; however, I had no intention whatever of offering
any annoyance to MR. TAYLOR in my remarks, which were intended solely with
a view to produce an effect which has partially been successful, that of
exciting a more definite explanation of his meaning. That MR. WELD TAYLOR
may "enlighten" me is not only possible, but very probable, and I can only
say I shall be much obliged to him for so doing.
With reference to his process for iodizing Canson's paper, I presume his
meaning to be as follows, viz.: Mix half an ounce of a _forty-grain_
solution of _nitrate of silver_ with an equal quantity {245} of a
_fifty-grain_ solution of _iodide of potassium_, by which a precipitate of
iodide of silver will be formed, the supernatant fluid containing the
excess of iodide of potassium and the nitrate of potash formed by the
decomposition. _Add_ drop by drop a solution of the cyanide of potassium,
until the iodide of silver is redissolved, and the liquid becomes limpid,
and then _four ounces_ more of distilled water, making up five ounces
altogether. The paper should then be washed over with the above and
_dried_, after which it may be floated on water slightly acidulated with
sulphuric acid for a few minutes, and after being again dried, either
wholly, or else partially with blotting-paper, may be rendered sensitive
with a weak solution of nitrate of silver. Here are two or three points
admitting doubt: first, Would it not be better to wash away the nitrate of
potash and free iodide of potash first, and then dissolve the iodide of
silver in solution of cyanide of potassium? Secondly, Would not a slight
soaking in plain water after the acidulated bath be of advantage? Thirdly,
Is it better to dry the paper again before rendering it sensitive? and
fourthly, What strength of nitrate of silver solution should be used to
render it sensitive; and ought it to have any acetic or gallic acid, or
both?